After CL 228645 some mentions of the Deadline methods referred
to the Timeout method, and some to os.ErrDeadlineExceeded.
Stop referring to the Timeout method, to encourage ErrDeadlineExceeded.
For #31449
Change-Id: I27b8ff34f31798f38b06437546886af8cce98ca4
Reviewed-on: https://go-review.googlesource.com/c/go/+/239705
Run-TryBot: Ian Lance Taylor <iant@golang.org> Reviewed-by: Damien Neil <dneil@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>